Semiconductor devices and methods

ABSTRACT

Semiconductor devices and their manufacturing methods are disclosed herein, and more particularly to semiconductor devices including a transistor having gate all around (GAA) transistor structures and manufacturing methods thereof. The methods described herein allow for complex shapes (e.g., “L-shaped”) to be etched into a multi-layered stack to form fins used in the formation of active regions of the GAA nanostructure transistor structures. In some embodiments, the active regions may be formed with a first channel width and a first source/drain region having a first width and a second channel width and a second source/drain region having a second width that is less than the first width.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No.62/927,531, filed on Oct. 29, 2019, which application is herebyincorporated herein by reference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as, for example, personal computers, cell phones, digital cameras,and other electronic equipment. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductor layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. However, asthe minimum features sizes are reduced, additional problems arise thatshould be addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1-12 illustrate intermediate steps in forming a gate-all-around(GAA) active device, in accordance with some embodiments.

FIG. 13A illustrates a perspective view of the GAA device, in accordancewith an embodiment.

FIG. 13B illustrates a top-down view through a cross section of the GAAdevice illustrated in FIG. 13A, in accordance with an embodiment.

FIGS. 14A and 14B illustrate top-down views through cross sections ofthe GAA device, in accordance with other embodiments.

FIGS. 15A to 15E illustrate top-down views of several cell schemescomprising arrays of multi-layer active devices, according to someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments will now be described with respect to the integration ofhorizontal gate-all-around (GAA) nanostructure transistors for use inthe design and operation of integrated circuits in the 3 nm technologynode and below. Such embodiments allow for complex shapes (e.g.,“L-shapes”) to be formed in active regions of the GAA nanostructuretransistors. According to the embodiments described herein, the GAA nanostructure transistors may be formed with a first channel width and afirst source/drain region having a first width and a second channelwidth and a second source/drain region having a second width that isless than the first width. As such, the GAA nanostructure transistorsmay be constructed with a complex active region (e.g., “L-shapes”) thatprovides power savings during operation and offers a flexible designwhich may be applied in various cell-type configurations. However,embodiments may be utilized in a wide variety of ways, and are notintended to be limited to the embodiments described herein.

With reference now to FIG. 1, there is illustrated a perspective view ofa deposition process 250 onto a substrate 101, in accordance with someembodiments, to form a multi-layer active device 200 in an intermediatestage of manufacturing the gate all-around (GAA) transistor. In anembodiment the substrate 101 is a semiconductor substrate, which may be,for example, a silicon substrate, a silicon germanium substrate, agermanium substrate, a III-V material substrate (e.g., GaAs, GaP, GaAsP,AlInAs, AlGaAs, GaInAs, InAs, GaInP, InP, InSb, and/or GaInAsP; or acombination thereof), or a substrate formed of other semiconductormaterials with, for example, high band-to-band tunneling (BTBT).Substrate 101 may be doped or un-doped. In some embodiments, substrate101 may be a bulk semiconductor substrate, such as a bulk siliconsubstrate that is a wafer, a semiconductor-on-insulator (SOI) substrate,a multi-layered or gradient substrate, or the like. The substrate 101may have dopants implanted in order to form wells for the formation ofactive devices.

FIG. 1 further illustrates that the substrate 101 comprises a firstdevice region 106 for forming n-type devices, such as NMOS transistors(e.g., n-type gate all around transistors), although the first deviceregion 106 may be used for forming p-type devices, such as PMOStransistors (e.g., p-type gate all around transistors). Although FIG. 1is illustrated as a single device region, it is understood that thefirst device region 106 is merely representative of a single area formedwithin a semiconductor wafer and the semiconductor wafer may comprisemany device regions. The many device regions may be formed aspluralities of the first device region 106 and/or pluralities of otherdevice regions different from the first device region 106.

FIG. 1 further illustrates a series of depositions that are performed toform a multi-layer stack 203 of alternating materials of first layers251 and second layers 261 over the substrate 101. According to someembodiments, the deposition process 250 comprises forming a first layer251 of semiconductor material with a first lattice constant, such asSiGe, Ge, Si, GaAs, InSb, GaSb, InAlAs, InGaAs, GaSbP, GaAsSb,combinations of these, or the like. In some embodiments, the first layer251 is epitaxially grown on the substrate 101 using a depositiontechnique such as epitaxial growth, vapor-phase epitaxy (VPE), molecularbeam epitaxy (MBE), although other deposition processes, such aschemical vapor deposition (CVD), low pressure CVD (LPCVD), atomic layerCVD (ALCVD), ultrahigh vacuum CVD (UHVCVD), reduced pressure CVD(RPCVD), a combination thereof, or the like, may also be utilized. Insome embodiments, the first layer 251 is formed to a first thickness Th1of between about 4 nm and about 15 nm, such as about 10 nm. However, anysuitable thickness may be utilized while remaining within the scope ofthe embodiments.

Once the first layer 251 has been formed over the substrate 101, thesecond layer 261 may be formed over the first layer 251. According tosome embodiments, the second layer 261 may be a second semiconductormaterial such as Si, SiGe, Ge, GaAs, InSb, GaSb, InAlAs, InGaAs, GaSbP,GaAsSb, combinations of these, or the like, with a different latticeconstant than the material of the first layer 251. In a particularembodiment in which the first layer 251 is silicon germanium, the secondlayer 261 is a material with a different lattice constant, such assilicon. However, any suitable combination of materials may be utilized.

In some embodiments, the second layer 261 is epitaxially grown on thefirst layer 251 using a deposition technique such as epitaxial growth,vapor-phase epitaxy (VPE), molecular beam epitaxy (MBE), although otherdeposition processes, such as chemical vapor deposition (CVD), lowpressure CVD (LPCVD), atomic layer CVD (ALCVD), ultrahigh vacuum CVD(UHVCVD), reduced pressure CVD (RPCVD), a combination thereof, or thelike, may also be utilized. The second layer 261 is formed to a secondthickness Th2 of between about 4 nm and about 10 nm, such as about 7 nm.However, any suitable material and any suitable thickness may be used.

Once the second layer 261 has been formed over the first layer 251, thedeposition process 250 is repeated to form the remaining material layersin the series of alternating materials of the first layers 251 and thesecond layers 261 until a desired topmost layer of the multi-layer stack203 has been formed. In a particular embodiment, another first layer 251is formed to a third thickness Th3, another second layer 261 is formedto a fourth thickness Th4, another first layer 251 is formed to a fifththickness Th5, and another second layer 261 is formed to a sixththickness Th6. Furthermore, the sheet spacing between the second layers261 are substantially equal to the thicknesses of the first layers 251(e.g., Th1, Th3, and Th5). According to the present embodiment, thetopmost layer of the multi-layer stack 203 is formed as a second layer261; however, in other embodiments, the topmost layer of the multi-layerstack 203 may be formed as a first layer 251. Additionally, althoughembodiments are disclosed herein comprising three first layers 251 andthree second layers 261, the multi-layer stack 203 may have any suitablenumber of layers (e.g., nanosheets). For example, the multi-layer stack203 may comprise multiple nanosheets in a range between 2 to 10nanosheets. In some embodiments, the multi-layer stack 203 may compriseequal numbers of first layers 251 to second layers 261; however, inother embodiments, the number of first layers 251 may be different fromthe number of second layers 261.

According to some embodiments, the first layers 251 of the multi-layerstack 203 are formed to be substantially a same thickness (e.g., thefirst thickness Th1˜the third thickness Th3˜the fifth thickness Th5) andthe thicknesses of the second layers 261 of the multi-layer stack 203are formed to substantially a same thickness (e.g., the second thicknessTh2˜the fourth thickness Th4˜the sixth thickness Th6). However, thethicknesses of the first layers 251 may be different thicknesses fromone another and/or the thickness of the second layers 261 may bedifferent thickness from one another. Any suitable thicknesses may beused.

With reference now to FIG. 2, there is illustrated a patterning process350 of the multi-layer active device 200 in an intermediate stage ofmanufacturing Gate All-Around (GAA) transistors, in accordance with someembodiments. The patterning process 350 may be utilized in an oxidedefinition step for transferring a desired shape (e.g., an “L-shaped”pattern) into the multi-layered stack 203 and substrate 101.

Once the multi-layer stack 203 has been formed over the substrate 101,the multi-layer stack 203 and substrate 101 may be patterned into adesired shape (e.g., “L-shape”), according to some embodiments. Thepatterning may be performed by initially forming a first hard mask 205and a second hard mask 207 over the first hard mask 205. The first hardmask 205 comprises a dielectric material such as silicon oxide, siliconnitride, titanium nitride, silicon oxynitride, combinations of these, orthe like. The first hard mask 205 may be formed using a process such aschemical vapor deposition, plasma enhanced chemical vapor deposition,atomic layer deposition, or the like. However, any other suitablematerial and method of formation may be utilized. The first hard mask205 may be formed to a thickness of between about 20 Å and about 3000 Å,such as about 20 Å.

The second hard mask 207 comprises a separate dielectric material suchas silicon nitride, silicon oxide, titanium nitride, silicon oxynitride,combinations of these, or the like. The second hard mask 207 may beformed using a process such as chemical vapor deposition, plasmaenhanced chemical vapor deposition, atomic layer deposition, or thelike. However, any other suitable material and method of formation maybe utilized. The second hard mask 207 may be formed to a thickness ofbetween about 20 Å and about 3,000 Å, such as about 20 Å.

Once the first hard mask 205 and the second hard mask 207 have beenformed, the first hard mask 205 and the second hard mask 207 may bepatterned. In an embodiment the first hard mask 205 and the second hardmask 207 may be patterned by initially placing a photoresist (notindividually illustrated) over the second hard mask 207 and exposing thephotoresist to a patterned energy source (e.g., light, such as, extremeultra-violet (EUV)) in order to initiate a chemical reaction thatmodifies the physical properties of the exposed portions of the firstphotoresist. The first photoresist may then be developed by applying afirst developer (also not individually illustrated) in order to utilizethe modified physical properties between the exposed region and theunexposed region to selectively remove either the exposed region or theunexposed region.

Once the photoresist has been patterned, the photoresist may be used asa mask in order to pattern the underlying second hard mask 207 and firsthard mask 205. In an embodiment the second hard mask 207 and the firsthard mask 205 may be patterned using, e.g., one or more reactive ionetching (RIE) processes with the photoresist as a mask. The patterningprocess may be continued until the multi-layer stack 203 is exposedbeneath the first hard mask 205.

Once the first hard mask 205 and the second hard mask 207 have beenpatterned, the photoresist may be removed from the second hard mask 207.In an embodiment the photoresist may be removed utilizing, e.g., anashing process, whereby a temperature of the photoresist is raised untilthe photoresist experiences a thermal decomposition and may be easilyremoved using one or more cleaning process. However, any other suitableremoval process may be utilized.

Using the first hard mask 205 and the second hard mask 207 as a mask inan oxide definition step, one or more etching processes such asanisotropic etching processes (e.g., reactive ion etching (RIE)) may beperformed to transfer the pattern of the mask (e.g., “L-shape”) into theunderlying layers to form a fin 122 in the multi-layer stack 203 andsubstrate 101. Although embodiments have been described as transferringan “L-shape” pattern into the multi-layer stack 203 and substrate 101 toform the fin 122, any suitable shapes may be utilized as is discussed ingreater detail below. Furthermore, any suitable etching process and anysuitable number of etching processes may be used in the oxide definitionstep to form the fin 122 in the multi-layer stack 203 and substrate 101.

Additionally, while a single mask process has been described to form thefin 122, this is intended to be illustrative and is not intended to belimiting, as the gate all around (GAA) transistor structures may bepatterned by any suitable method and any suitable number of fins may beformed in the multi-layer stack 203 and substrate 101. For example, thestructures may be patterned using one or more photolithographyprocesses, including double-patterning or multi-patterning processes andmany fins having the same “L-shape” pattern of the fin 122 or any othersuitable shape may be formed. Generally, double-patterning ormulti-patterning processes combine photolithography and self-alignedprocesses, allowing patterns to be created that have, for example,pitches smaller than what is otherwise obtainable using a single, directphotolithography process. For example, in one embodiment, a sacrificiallayer is formed over a substrate and patterned using a photolithographyprocess. Spacers are formed alongside the patterned sacrificial layerusing a self-aligned process. The sacrificial layer is then removed, andthe remaining spacers may then be used to pattern the fin 122 in themulti-layer stack 203 and substrate 101.

Turning to FIG. 3, after the formation of the fin 122, STI region 135(e.g., shallow trench isolation region) is formed. In an embodiment, theSTI region 135 may be formed by depositing a dielectric material such asan oxide material (e.g., a flowable oxide), high-density plasma (HDP)oxide, or the like. The dielectric material may be formed, after anoptional cleaning and lining, using chemical vapor deposition (CVD)methods (e.g., the HARP process), high density plasma CVD methods, orother suitable methods of formation to fill or overfill the regionsaround the fin 122.

Once deposited, excess dielectric material of the STI region 135 may beremoved through a suitable process such as chemical mechanical polishing(CMP), etching, a combination of these, or the like. In an embodiment,the removal process removes any dielectric material that is located overthe fin 122 as well, so that the removal of the dielectric material willexpose the surface of the fin 122 to further processing steps.

With the excess dielectric material of the STI region 135 having beenremoved, the dielectric material may then be recessed away from thesurface of the fin 122 to form the STI region 135. The recessing may beperformed to expose at least a portion of the sidewalls of the fin 122adjacent to the top surface of the fin 122. The dielectric material ofthe STI region 135 may be recessed using a wet etch by dipping the topsurface of the fin 122 into an etchant selective to the dielectricmaterial, although other methods, such as a reactive ion etch, a dryetch, chemical oxide removal, or dry chemical clean may be used. In someembodiments, the dielectric material may be recessed below thebottommost layer of the first layers 251 to expose some of the substrate101.

FIG. 3 further illustrates an active region 301 of the fin 122 having afirst length L1 between corners 303 of the “L-shape.” According to someembodiments, the first length L1 may be between about 8 nm and about 30nm, such as about 10 nm. However, any suitable length may be used.

At distal ends of the active region 301, the fin 122 has a first widthW1 and a second width W2 different from the first width W1. According tosome embodiments, the second width W2 is less than the first width W1,although the second width W2 may also be greater than the first widthW1. The first width W1 may be between about 8 nm and about 50 nm, suchas about 30 nm. The second width W2 may be between about 8 nm and about50 nm, such as about 10 nm. In some embodiments, a difference betweenthe first width W1 and the second width W2 may be between about 2 nm andabout 16 nm, such as about 10 nm, and a first ratio R1 between the firstwidth W1 and the second width W2 which may be between about 4:1 andabout 1.5:1, such as about 3:1. However, any suitable widths and anysuitable ratios may be utilized.

FIG. 4 illustrates the formation of a dummy gate stack 129 over theactive region 301 and between the corners 303 of the “L-shape” in thefin 122. According to some embodiments, the dummy gate stack 129comprises a dummy gate dielectric 119, a dummy gate electrode 121 overthe dummy gate dielectric 119, a third hard mask 123 over the dummy gateelectrode 121, and a fourth hard mask 125 over the third hard mask 123.FIG. 4 further illustrates a left-side interface between the dummy gatestack 129 and the active region 301 having a third width W3 and aright-side interface between the dummy gate stack 129 and the activeregion 301 having a fourth width W4.

In an embodiment the dummy gate dielectric 119 may be formed by thermaloxidation, chemical vapor deposition, sputtering, or any other methodsknown and used in the art for forming a gate dielectric. Depending onthe technique of gate dielectric formation, the dummy gate dielectric119 thickness on the top of the fin 122 may be different from thethickness of the dummy gate dielectric 119 on the sidewalls of the fin122. The dummy gate dielectric 119 may comprise a material such assilicon dioxide or silicon oxynitride with a thickness ranging fromabout 3 angstroms to about 100 angstroms, such as about 10 angstroms. Inan embodiment the dummy gate dielectric 119 may be formed by firstdepositing a sacrificial layer of a material such as silicon in order toprovide sidewall protection. Once the sacrificial layer has been formedthe sacrificial material may be oxidized or nitridized and consumed inorder to form a dielectric such as the silicon dioxide or siliconoxynitride. However, any suitable process may be utilized.

In other embodiments the dummy gate dielectric 119 may also be formedfrom a high permittivity (high-k) material (e.g., with a relativepermittivity greater than about 5) such as lanthanum oxide (La₂O₃),aluminum oxide (Al₂O₃), hafnium oxide (HfO₂), hafnium oxynitride (HfON),or zirconium oxide (ZrO₂), or combinations thereof, with an equivalentoxide thickness of about 0.5 angstroms to about 100 angstroms, such asabout 10 angstroms or less. Additionally, any combination of silicondioxide, silicon oxynitride, and/or high-k materials may also be usedfor the dummy gate dielectric 119.

The dummy gate electrode 121 may comprise a conductive material and maybe selected from a group comprising polysilicon, W, Al, Cu, AlCu, W, Ti,TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN, Ta, TaN, Co, Ni, combinations ofthese, or the like. The dummy gate electrode 121 may be deposited bychemical vapor deposition (CVD), sputter deposition, or other techniquesknown and used in the art for depositing conductive materials. Thethickness of the dummy gate electrode 121 may be in the range of about 5Å to about 500 Å. The top surface of the dummy gate electrode 121 mayhave a non-planar top surface, and may be planarized prior to patterningof the dummy gate electrode 121 or the gate etch. Ions may or may not beintroduced into the dummy gate electrode 121 at this point. Ions may beintroduced, for example, by ion implantation techniques.

Once the dummy gate dielectric 119 and the dummy gate electrode 121 havebeen formed, the dummy gate dielectric 119 and the dummy gate electrode121 may be patterned. In an embodiment the patterning may be performedby initially forming the third hard mask 123 and the fourth hard mask125 over the third hard mask 123. The third hard mask 123 and the fourthhard mask 125 may be formed using any of the materials and processessuitable for forming the first hard mask 205 and the second hard mask207, respectively. According to some embodiments, the third hard mask123 is formed as a layer of silicon oxide to a thickness of betweenabout 20 Å and about 3000 Å, such as about 20 Å and, in someembodiments, the fourth hard mask 125 may be formed as a layer ofsilicon nitride to a thickness of between about 20 Å and about 3000 Å,such as about 20 Å. However, any suitable materials and thickness may beused.

Once the third hard mask 123 and the fourth hard mask 125 have beenformed, the third hard mask 123 and the fourth hard mask 125 may bepatterned using any of the materials (e.g., photoresist) and processes(e.g., exposing and developing the photoresist, reactive ion etching(RIE), and the like) suitable for patterning the first hard mask 205 andthe second hard mask 207, as set forth above. The patterning process maybe continued until the dummy gate electrode 121 is exposed beneath thethird hard mask 123.

Once the third hard mask 123 and the fourth hard mask 125 have beenpatterned, the photoresist may be removed from the third hard mask 123and the fourth hard mask 125 (e.g., using an ashing process). However,any other suitable removal process may be utilized. Using the third hardmask 123 and the fourth hard mask 125 as a mask and using an anisotropicetching process (e.g., reactive ion etching (RIE)), the pattern of thethird hard mask 123 and the fourth hard mask 125 is transferred to thedummy gate electrode 121 and the dummy gate dielectric 119 in order toform the dummy gate stack 129 over the fin 122, although any suitableprocess for transferring a pattern into dielectric layers, as set forthabove with regard to the first hard mask 205 and the second hard mask207 may also be utilized.

Once the dummy gate stack 129 has been formed, the upper surface and thesidewalls of the multi-layer stack 203 and the upper surface of the STIregion 135 that are not protected by the dummy gate stack 129 arere-exposed. In an embodiment, the dummy gate stack 129 may be formed tocover a portion of the multi-layer stack 203 with a dummy gate widthW_(dg) that is less than first length L1, such has the dummy gate widthW_(dg) being between about 8 nm and about 16 nm, such as about 10 nm. Assuch, the dummy gate electrode will form a left-side interface and aright side interface with the multi-layer stack 203. According to someembodiments, the third width W3 of the active region 301 at theleft-side interface may be between about 28 nm and about 34 nm, such asabout 30 nm and the fourth width W4 of the active region 301 at theright-side interface may be between about 8 nm and about 12 nm, such asabout 10 nm. However, any suitable widths may be used.

FIG. 5 illustrates the formation of a conformal dielectric layer 130, inaccordance with some embodiments. The conformal dielectric layer 130 isdeposited over the dummy gate stack 129, the fin 122, and the STI region135 in an initial step of forming gate spacers 131 for a gate electrode1103. As such, the conformal dielectric layer 130 is formed on opposingsides of the dummy gate stack 129 along sidewalls of the dummy gatedielectric 119, the dummy gate electrode 121, the third hard mask 123,and the fourth hard mask 125. The conformal dielectric layer 130 is alsoformed on opposing sides of the fin 122 along sidewalls of the firstlayers 251 and the second layers 261 and any exposed portions of thesubstrate 101. The portions of the active region 301 and the corners 303of the “L-shape” in the fin 122 are disposed under the conformaldielectric layer 130 and are therefore not illustrated in FIG. 5.

The conformal dielectric layer 130 may be formed by blanket depositionon the multi-layer active device 200, according to some embodiments. Theconformal dielectric layer 130 may comprise silicon oxide (SiO₂),silicon oxynitride (SiON), silicon nitride (Si₃N₄), silicon oxycarbide(SiOC), silicon oxycarbonitride (SiOCN), although any suitable material,such as low-k materials with a k-value less than about 4.0, or even anair gap, or combination thereof may be utilized. The conformaldielectric layer 130 may be formed by any suitable methods utilized toform such a layer, such as chemical vapor deposition (CVD), plasmaenhanced CVD, sputter, and any other suitable methods.

FIG. 6 illustrates an etching of horizontal surfaces of the conformaldielectric layer 130 in order to form the gate spacers 131 on the dummygate stack 129. In an embodiment the gate spacers 131 may be formedusing an anisotropic etching process such as a reactive ion etching(RIE) process. However, while the gate spacers 131 are described using asingle layer as the conformal dielectric layer 130, this is intended tobe illustrative and is not intended to be limiting. Rather, any numberof layers and any combinations of deposition and removal processes maybe used, and all such processes are fully intended to be included withinthe scope of the embodiments. Once the horizontal surfaces of theconformal dielectric layer 130 have been removed, the topmost surfacesof the fourth hard mask 125, the fin 122, and the STI region 135 thatare not protected by the vertical sidewalls of the gate spacers 131 andthe dummy gate stack 129 are re-exposed.

Once the gate spacers 131 have been formed, trenches 133 may be etchedthrough the fin 122 using an etching process performed to removematerials of the fin 122 that are exposed on either side of the dummygate stack 129 and are not protected by the sidewalls of the gatespacers 131. According to some embodiments, the trenches 133 may beetched using one or more anisotropic etches, such as reactive ion etchesto etch through the fin 122 and may be formed with dimensions of theportions of the fins 122 that they displace.

In some embodiments, a first trench that is formed on a left side of thedummy gate stack 129 may be formed with the first width W1 at the distalend of the trench 133 from the exposed sidewall of the fin 122 and maybe formed with a fifth width W5 at the exposed sidewall of the fin 122.The fifth width W5 is less than or equal to the first width W1 (e.g.,between about 8 nm and about 50 nm, such as about 30 nm) and is greaterthan the third width W3 (e.g., between about 8 nm and about 50 nm, suchas about 28 nm). However, any suitable widths may be utilized.

According to some embodiments, a second trench that is formed on a rightside of the dummy gate stack 129 may be formed with the second width W2at the distal end of the trench 133 from the exposed sidewall of the fin122 and may be formed with a sixth width W6 at the exposed sidewall ofthe fin 122. The sixth width W6 is greater than or equal to the secondwidth W2 (e.g., between about 8 nm and about 50 nm, such as about 10 nm)and is less than the fourth width W4 (e.g., between about 8 nm and about50 nm, such as about 20 nm). However, any suitable widths may beutilized.

FIG. 7 illustrates formation of first inner spacers 501 in the firstlayers 251 (shown in FIG. 6) of the first device region 106. The firstinner spacers 501 are formed in the recesses of the first layers 251 inthe first device region 106. In some embodiments, the first innerspacers 501 are formed by patterning recesses using a wet etch with anetchant selective to the material of the first layers 251 (e.g., silicongermanium (SiGe)) without significantly removing the material of thesecond layers 261 (e.g., silicon) or the substrate 101 (e.g., Si). Forexample, in an embodiment in which the first layers 251 are silicongermanium and the second layers 261 are silicon, the wet etch may use anetchant such as hydrochloric acid (HCl).

In an embodiment the wet etching process may be a dip process, a sprayprocess, a spin-on process, or the like. Additionally, the wet etchingprocess may be performed at a temperature of between about 400° C. andabout 600° C. and may be continued for a time of between about 100seconds and about 1000 seconds, such as about 300 seconds. However, anysuitable process conditions and parameters may be utilized. The etchingprocess may be continued such that recesses with facet limited surfacesare formed in each of the first layers 251 to a length of between about4 nm and about 8 nm, such as about 6 nm. However, any suitable lengthmay be used.

However, a wet etching process is not the only process that may beutilized. For example, in another embodiment the patterning of the firstlayers 251 may be performed with an isotropic dry etching process or acombination of a dry etching process and a wet etching process. Anysuitable process of patterning the first layers 251 may be utilized, andall such processes are fully intended to be included within the scope ofthe embodiments.

Once the recesses are formed in each of the first layers 251 in thefirst device region 106, a spacer material is formed over both the firstdevice region 106. In some embodiments, the spacer material can bedifferent from the material of the gate spacers 131 and can be adielectric material comprising silicon such as silicon oxide (SiO₂),silicon oxynitride (SiON), silicon nitride (Si₃N₄), silicon oxycarbide(SiOC), silicon oxycarbonitride (SiOCN), although any suitable materialsuch as low-k materials with a k-value less than about 4.0, or even anair gap, or combination thereof may also be utilized. The spacermaterial may be deposited using a deposition process such as chemicalvapor deposition, physical vapor deposition, or atomic layer depositionto a thickness of between about 3 nm and about 10 nm, such as about 5nm. However, any suitable thickness or deposition process may beutilized.

By depositing the spacer material over the first device region 106, thespacer material will line the sidewalls of the trenches 133 and willalso fill in the recesses in the first layers 251 of the first deviceregion 106. Once the recesses have been filled with the spacer material,a removal process is then performed to remove the excess spacer materialfrom the trenches 133 within the first device region 106, while leavingbehind first inner spacers 501 in the first device region 106. In anembodiment, the removal of the excess spacer material may be performedusing an etching process such as, e.g., an anisotropic, dry etchingprocess such as a reactive ion etching process. However, any suitableetching process, which removes the excess spacer material from thetrenches 133 while leaving behind the first inner spacers 501 and theother inner spacers, may be utilized.

As such, the first inner spacers 501 will take on the shape of the firstrecesses. Additionally, while an embodiment forming the first innerspacers 501 to faceted shapes is described, this is intended to beillustrative and is not intended to be limited. Rather, any suitableshape, such as a concave shape or a convex shape, or even recessesformed in the first inner spacers 501 may be utilized. All such shapesare fully intended to be included within the scope of the embodiments.

FIG. 8 illustrates formation of source/drain regions 601 within thefirst device region 106. Based on the different widths (e.g., the firstwidth W1, the second width W2, the third width W3, the fourth width W4,the fifth width W5, and the sixth width W6) of the left side and rightside of the active region 301, the source/drain regions 601 are formedwith unbalanced widths. For example, according to some embodiments, thesource/drain regions 601 located on the left side of the dummy gatestack 129 is formed to a seventh width W7 and the source/drain region601 located on the right side of the dummy gate stack 129 is formed toan eighth width W8, where W7 is greater than W8. According to someembodiments, the source/drain regions 601 located on the left side ofthe dummy gate stack 129 are formed to the seventh width W7 of betweenabout 8 nm and about 50 nm, such as about 30 nm and the source/drainregion 601 located on the right side of the dummy gate stack 129 isformed to the eighth width W8 of between about 8 nm and about 50 nm,such as about 10 nm.

In an embodiment the source/drain regions 601 may be formed by initiallyprotecting the other device regions with, for example, a photoresist orother masking materials. Once the other device regions have beenprotected, the source/drain regions 601 may be formed using a growthprocess such as a selective epitaxial process with a semiconductormaterial suitable for the device desired to be formed. For example, inan embodiment in which the source/drain regions 601 are utilized to forman NMOS device, the source/drain regions 601 may be a semiconductormaterial such as silicon, silicon phosphorous, silicon carbonphosphorous, combinations, of these, or the like. The epitaxial growthprocess may use precursors such as silane, dichlorosilane, germane, andthe like, and may continue for between about 5 minutes and about 120minutes, such as about 30 minutes. According to some embodiments, thesource/drain regions 601 are formed to a first source/drain height SDH1of between about 30 nm and about 90 nm, such as about 60 nm. However,any suitable heights and/or suitable depths may be used.

Once the source/drain regions 601 are formed, dopants may be implantedinto the source/drain regions 601 by implanting appropriate dopants tocomplement the dopants within the remainder of the first device region106. For example, n-type dopants such as phosphorous (P), carbon (C),arsenic (As), silicon (Si), antimony (Sb), or the like, and combinationsthereof (e.g., SiP, SiC, SiPC, SiAs, Si, Sb, etc.) may be implanted toform NMOS devices. These dopants may be implanted using the dummy gatestack 129 and the gate spacers 131 as masks.

In another embodiment, the dopants of the source/drain regions 601 maybe placed during the growth of the source/drain regions 601. Forexample, phosphorous may be placed in situ as the source/drain regions601 are being formed. Any suitable process for placing the dopantswithin the source/drain regions 601 may be utilized, and all suchprocesses are fully intended to be included within the scope of theembodiments. Furthermore, an anneal process may be performed to activatethe dopants within the source/drain regions 601.

In FIG. 9, a contact etch stop layer (CESL) 87 is deposited over thestructure illustrated in FIG. 8. The CESL 87 may comprise a dielectricmaterial with silicon, nitride, and an additional element, such ascarbon also added to the material, such as silicon carbon nitride(SiCN). In some embodiments the CESL 87 comprises a dielectric material,such as silicon oxide, silicon nitride or any other suitable dielectricmaterial, or the like. However, any suitable materials may be utilized.

The dielectric material of the CESL 87 (e.g., SiCN) may be conformallydeposited over the source/drain regions 601, the fourth hard mask 125,and the gate spacers 131 of the structure shown in FIG. 8. According tosome embodiments, the CESL 87 may be formed using a chemical vapordeposition (CVD) process, although any suitable deposition process maybe utilized.

FIG. 9 further illustrates an interlayer dielectric (ILD) 701 that isdeposited over the CESL 87. The ILD 701 may be formed of a dielectricmaterial, and may be deposited by any suitable method, such as CVD,plasma-enhanced CVD (PECVD), or flowable chemical vapor deposition(FCVD). Dielectric materials may include phospho-silicate glass (PSG),boro-silicate glass (BSG), boron-doped phospho-silicate glass (BPSG),undoped silicate glass (USG), or the like. Other insulation materialsformed by any acceptable process may be used.

FIG. 9 further illustrates that a planarization process, such as a CMP,may be performed to level the top surface of the ILD 701 with the topsurfaces of the dummy gate electrode 121, the gate spacers 131, and theCESL 87. As such, the planarization process also removes the third hardmask 123 and the fourth hard mask 125 and exposes the top surface of thedummy gate electrode 121 between the gate spacers 131. After theplanarization process, top surfaces of the dummy gates 72, the gatespacers 131, and the ILD 701 are level. In some embodiments, the thirdhard mask 123 (or a portion of the third hard mask 123) may remain overthe top surface of the dummy gate electrode 121, in which case theplanarization process levels the top surface of the ILD 701, the gatespacers 131, and the CESL 87 with the top surface of the third hard mask123.

FIG. 10 illustrates a removal of the dummy gate electrode 121, the dummygate dielectric 119 and (if remaining) removal of any remaining portionof the third hard mask 123. As such, a central portion of the activeregion 301 is exposed in an opening 1033 between the gate spacers 131,whereas other portions of the active region 301 and the corners 303 ofthe “L-shape” in the fin 122 remain covered by the gate spacers 131.FIG. 10 further illustrates the gate spacers 131 in phantom to showdistal ends of the second layers 261 and the first inner spacers 501being embedded in the gate spacers 131 and to show the first innerspacers 501 separating the distal ends of the second layers 261 from oneanother.

In an embodiment any remaining portion of the third hard mask 123 may beremoved using an etching process or a planarization process (e.g., acontinuation of the previous chemical mechanical polishing process) toremove the material of the third hard mask 123. However, any suitablemethod of removing the third hard mask 123 may be utilized. Once thehard mask 123 has been removed, the dummy gate electrode 121 is exposedand can then be removed. In an embodiment the dummy gate electrode 121may be removed using, e.g., one or more wet or dry etching processesthat utilize etchants that are selective to the material of the dummygate electrode 121. However, any suitable removal process may beutilized. Once the dummy gate electrode 121 has been removed, the dummygate dielectric 119 is exposed and can also be removed. In anembodiment, the dummy gate dielectric 119 is removed using, e.g., one ormore wet or dry etching processes that utilize etchants that areselective to the material of the dummy gate dielectric 119. As such,upper surfaces of the STI region 135, an upper surface of a topmostlayer of the second layers 261, sides of the first layers 251, sides ofthe second layers 261, sides of the substrate 101 (above the STI region135) and sidewalls of the gate spacers 131 are exposed in the centralportion of the active region 301.

FIG. 11 illustrates a wire release process step. The wire releaseprocess step may also be referred to as a sheet release process step, asheet formation process step, a nanosheet formation process step or awire formation process step. Once the dummy gate dielectric 119 has beenremoved (which also exposes the sides of the first layers 251), thefirst layers 251 may be removed from between the substrate 101 and frombetween the second layers 261 within both the first device region 106.In an embodiment the first layers 251 may be removed using a wet etchingprocess that selectively removes the material of the first layers 251(e.g., silicon germanium (SiGe)) without substantively removing thematerial of the substrate 101 and the material of the second layers 261(e.g., silicon (Si)). However, any suitable removal process may beutilized. In an embodiment, the etchant may be a high temperature HCl.Additionally, the wet etching process may be performed at a temperatureof between about 400° C. and about 600° C., such as about 560° C., andfor a time of between about 100 seconds and about 600 seconds, such asabout 300 seconds. However, any suitable etchant, process parameters,and time can be utilized.

By removing the material of the first layers 251, the material of thesecond layers 261 (e.g., nanosheets) are formed into nanostructures 901within the first device region 106 separated from each other by thefirst inner spacers 501. The nanostructures 901 stretch between oppositeones of the source/drain regions 601 (shown in FIG. 8) and collectivelyform a stack of channel regions of the gate all-around (GAA) transistorbeing formed within the first device region 106. In an embodiment, thenanostructures 901 are formed to have same thicknesses as the originalthicknesses of the second layers 261.

In other embodiments, however, the etching process may also be utilizedto reduce a thickness of a portion of the nanostructures 901 such thatthe thickness of the nanostructures 901 may be different as the widthchanges. In particular, the thicknesses for the nanostructures 901 maybe thinner than the original thicknesses of the second layers 261 (e.g.,Si) by about 0.3 nm and about 2 nm. For example, during the wire releaseprocess step and during the formation of the gate dielectric 1101, thethicknesses of each of the second layers 261 may experience some Simaterial loss and/or oxidation. As such, each of the nanostructures 901and, hence the central portion of the active region 301, are formed to athickness of between about 4 nm and about 8 nm, such as about 5 nm andare spaced apart by their original spacing (e.g., Th1, Th2, and Th3)plus any additional space (e.g., about 0.3 nm and about 2 nm) created bySi material loss and/or oxidation during the wire release process stepand during the formation of the gate dielectric 1101. However, thecorners 303 of the “L-shape” in the fin 122 and the other portions ofthe active region 301 remain protected by the gate spacers 131 duringthe wire release step and during the formation of the gate dielectric1101. Accordingly, the corners 303 of the “L-shape” in the fin 122 andthe other portions of the active region 301 protected by the gatespacers 131 retain their original thicknesses.

Additionally, although FIG. 11 illustrates the formation of three of thenanostructures 901, any suitable number of the nanostructures 901 may beformed from the nanosheets provided in the multi-layer stack 203. Forexample, the multi-layer stack 203 (shown in FIG. 1) may be formed toinclude any suitable number of first layers 251 (e.g., first nanosheets)and any suitable number of second layers 261 (e.g., second nanosheets).As such, a multi-layer stack 203 that comprises fewer first layers 251and fewer second layers 261, after removal of the first layers 251,forms one or two of the nanostructures 901 as the stack of channelregions of the GAA transistor being formed within the first deviceregion 106. Whereas, a multi-layer stack 203 that comprises many of thefirst layers 251 and many of the second layers 261, after removal of thefirst layers 251, forms four or more of the nanostructures 901 as thestack of channel regions of the GAA transistor being formed within thefirst device region 106. FIG. 11 further illustrates the central regionof the active region 301 being exposed while the other portions of theactive region 301 and the corners 303 of the “L-shape” in the fin 122remain protected by the gate spacers 131.

FIG. 12 illustrates the formation of a gate dielectric 1101 within thefirst device region 106, in accordance with some embodiments. Once thewire release process step has been formed and the nanostructures 901have been exposed, the gate dielectric 1101 may be formed around thenanostructures 901. In some embodiments, prior to the formation of thegate dielectric 1101, an optional first interface layer (not separatelyillustrated) may be formed to surround the exposed surfaces of thenanostructures 901, the substrate 101, the STI region 135 and the gatespacers 131 within the opening 1033 between the gate spacers 131 andcover the top surfaces of the gate spacers 131, the CESL 87, and the ILD701. In some embodiments, the optional first interface layer comprises abuffer material such as silicon oxide (SiO_(x)), although any suitablematerial may be utilized. The optional first interface layer may beformed around the nanostructures 901 in the first device region 106using a process such as CVD, PVD, or even oxidation to a thickness ofbetween about 1 {acute over (Å)} and about 20 {acute over (Å)}, such asabout 9 {acute over (Å)}. However, any suitable process or thicknessesmay be utilized.

In an embodiment the gate dielectric 1101 is a high-k dielectricmaterial such as HfO₂, HfSiO, HfSiON, HfTaO, HfTiO, HfZrO, LaO, ZrO,TiO, Ta₂O₅, Al₂O₃, combinations of these, or the like, deposited througha process such as atomic layer deposition, chemical vapor deposition, orthe like. The gate dielectric 1101 may be deposited to a thickness ofbetween about 1 nm and about 3 nm, although any suitable material andthickness may be utilized. As illustrated, the gate dielectric 1101wraps around the nanostructures 901, thus isolating the stack of channelregions of the GAA transistor being formed within the first deviceregion 106. In some embodiments, an optional nitrogen doped dielectricmaterial (not illustrated) may be initially formed prior to forming themetal content material of a gate electrode over the gate dielectric1101, as is described in greater detail below.

FIG. 13A illustrates the formation of a gate electrode 1103 for an“L-shaped” GAA transistor 1300 formed within the first device region106, in accordance with some embodiments. The gate electrode 1103, thegate spacers 131, the CESL 87, and the ILD 701 are illustrated in FIG.13A using a phantom view to allow certain features embedded within the“L-shaped” GAA transistor 1300 to be seen. For example, the portions ofthe active region 301, the source/drain regions 601, portions of thenanostructures 901, the first inner spacers 501, and the gate dielectric1101 that are embedded in the gate electrode 1103, the gate spacers 131,the CESL 87, and the ILD 701 may be viewed in the “L-shaped” GAAtransistor 1300 illustrated in FIG. 13A. FIG. 13A further illustratesthe seventh width W7 of the source/drain region 601 on the left side ofthe “L-shaped” GAA transistor 1300 and the eighth width W8 of thesource/drain region 601 on the right side of the “L-shaped” GAAtransistor 1300.

Once the gate dielectric 1101 has been formed around the nanostructures901, the gate electrode 1103 may be formed over the gate dielectric 1101and filling in the remaining space of the opening 1033 between the gatespacers 131. In an embodiment the gate electrode 1103 is formed usingmultiple layers, each layer deposited sequentially adjacent to eachother using a highly conformal deposition process such as atomic layerdeposition, although any suitable deposition process may be utilized. Assuch, the multiple layers used to form the gate electrode 1103 fill theopen areas remaining between the stack of channel regions isolated bythe gate dielectric 1101 and fill other open areas remaining in theopening 1033. According to some embodiments, the gate electrode 1103 maycomprise a capping layer, a barrier layer, an n-metal work functionlayer, a p-metal work function layer, and a fill material (notseparately illustrated).

The capping layer may be formed adjacent to the gate dielectric 1101 andmay be formed from a metallic material such as TaN, Ti, TiAlN, TiAl, Pt,TaC, TaCN, TaSiN, Mn, Zr, TiN, Ru, Mo, WN, other metal oxides, metalnitrides, metal silicates, transition metal-oxides, transitionmetal-nitrides, transition metal-silicates, oxynitrides of metals, metalaluminates, zirconium silicate, zirconium aluminate, combinations ofthese, or the like. The metallic material may be deposited using adeposition process such as atomic layer deposition, chemical vapordeposition, or the like, although any suitable deposition process may beused.

The barrier layer may be formed adjacent the capping layer, and may beformed of a material different from the capping layer. For example, thebarrier layer may be formed of a material such as one or more layers ofa metallic material such as TiN, TaN, Ti, TiAlN, TiAl, Pt, TaC, TaCN,TaSiN, Mn, Zr, Ru, Mo, WN, other metal oxides, metal nitrides, metalsilicates, transition metal-oxides, transition metal-nitrides,transition metal-silicates, oxynitrides of metals, metal aluminates,zirconium silicate, zirconium aluminate, combinations of these, or thelike. The barrier layer may be deposited using a deposition process suchas atomic layer deposition, chemical vapor deposition, or the like,although any suitable deposition process may be used.

According to some embodiments, the GAA transistor being formed withinthe first device region 106 may be a first type of GAA transistor (e.g.,NMOS). As such, the n-metal work function layer may be formed adjacentto the barrier layer. In an embodiment the n-metal work function layeris a material such as W, Cu, AlCu, TiAlC, TiAlN, TiAl, Pt, Ti, TiN, Ta,TaN, Co, Ni, Ag, Al, TaAl, TaAlC, TaC, TaCN, TaSiN, Mn, Zr, othersuitable n-type work function materials, or combinations thereof. Forexample, the first n-metal work function layer may be depositedutilizing an atomic layer deposition (ALD) process, CVD process, or thelike. However, any suitable materials and processes may be utilized toform the n-metal work function layer.

The p-metal work function layer may be formed adjacent to the n-metalwork function layer. In an embodiment, the first p-metal work functionlayer may be formed from a metallic material such as W, Al, Cu, TiN, Ti,TiAlN, TiAl, Pt, Ta, TaN, Co, Ni, TaC, TaCN, TaSiN, TaSi₂, NiSi₂, Mn,Zr, ZrSi₂, TaN, Ru, AlCu, Mo, MoSi₂, WN, other metal oxides, metalnitrides, metal silicates, transition metal-oxides, transitionmetal-nitrides, transition metal-silicates, oxynitrides of metals, metalaluminates, zirconium silicate, zirconium aluminate, combinations ofthese, or the like. Additionally, the p-metal work function layer may bedeposited using a deposition process such as atomic layer deposition,chemical vapor deposition, or the like, although any suitable depositionprocess may be used.

Once the p-metal work function layer has been formed, the fill materialis deposited to fill the remainder of the opening 1033. In an embodimentthe fill material may be a material such as tungsten, Al, Cu, AlCu, W,Ti, TiAlN, TiAl, Pt, TaC, TaCN, TaSiN, Mn, Zr, TiN, Ta, TaN, Co, Ni,combinations of these, or the like, and may be formed using a depositionprocess such as chemical vapor deposition, atomic layer deposition,physical vapor deposition, plating, combinations of these, or the like.However, any suitable material may be utilized.

Once the openings 1033 left behind by the removal of the dummy gateelectrode 121 have been filled, the materials of the gate electrode 1103in the first device region 106 may be planarized in order to remove anymaterial that is outside of the openings left behind by the removal ofthe dummy gate electrodes 121. In a particular embodiment the removalmay be performed using a planarization process such as chemicalmechanical polishing. However, any suitable planarization and removalprocess may be utilized.

FIG. 13B illustrates a top-down view through the cut-line A-A of the“L-shaped” GAA transistor 1300 in FIG. 13A, in accordance with anembodiment. In particular, FIG. 13B illustrates the gate electrode 1103,the gate spacers 131, and the active region 301 within the channelregion of the “L-shaped” GAA transistor 1300. FIG. 13B furtherillustrates features of the active region 301 including: the corners303, the seventh width W7 of the left-side source/drain region 601, theeighth width W8 of the right-side source/drain region 601, and the firstlength L1, according to some embodiments. For ease of discussion, thegate dielectric 1101 and the CESL 87 are not shown.

With further regard to FIG. 13B, this figure also illustrates that the“L-shaped” GAA transistor 1300 is formed, according to some embodiments,with the gate electrode 1103 disposed directly over and aligned with the“L-shaped” active region 301 such that the corners 303 of the “L-shape”in the fin 122 are disposed beneath the gate electrode 1103 at theinterfaces between the stack of the nanostructures 901 and thesource/drain regions 601. Furthermore, FIG. 13B illustrates that theinterface at the left side of the active region 301 (e.g., left-sidechannel width) has the third width W3 and the interface at the rightside of the active region 301 (e.g., right-side channel width) has thefourth width W4, wherein the third width W3 is greater than the fourthwidth W4. FIG. 13B further illustrates a left-side channel interfacebetween the left side distal ends of the nanostructures 901 and thesource/drain region 601 having, e.g., the fifth width W5 and aright-side channel interface between the right side distal ends of thenanostructures 901 and the source/drain region 601 having, e.g., thesixth width W6.

Such multi-layer active devices 200 comprising the “L-shaped” activeregion with a width of one side of the active region 301 being greaterthan a width of the other side of the active region 301 may provide apower savings benefit as compared to an active device 200 having anactive region 301 with no difference between widths of the one side andthe other. For example, the “L-shaped” GAA transistor 1300 may be formedwith the active region 301 having the left-side channel width beinggreater than the right-side channel width (e.g., W3>W4) may provide apower saving benefit of between about 6% and about 8%. Furthermore,multi-layer active devices 200 comprising the “L-shaped” active region301 may be formed with channel interfaces to about the same width of thechannel widths of the active region 301 (e.g., W5˜W3 and/or W6˜W4). Assuch, the source/drain regions 601 may be formed with little to nodistortion at their interfaces with the stack of nanostructures 901 inthe active region 301.

FIG. 14A illustrates a top-down view through the cut-line A-A of the“L-shaped” GAA transistor 1300 in FIG. 13A, in accordance with anotherembodiment. FIG. 14A is similar to and illustrates the same features asFIG. 13B; however, in FIG. 14A the gate electrode 1103, gate dielectric1101 (not shown), and gate spacers 131 are formed over the active region301 with an offset to the left (OS-L), according to some embodiments.For ease of discussion, the gate dielectric 1101 and the CESL 87 are notshown.

According to some embodiments, the offset to the left (OS-L) is betweenabout 0 nm and about 8 nm and may be formed by shifting the design ofthe photoresist masks or else through the use of measured overlayshifts. The left-side channel width and the right side-channel width ofthe active region 301 appear shifted to the left of the corners 303 ofthe “L-shape” in the fin 122 by the distance of the offset to the left(OS-L) with respect to each of the corners 303. As such, the corner 303on the left side of the multi-layer active device 200 is located beneaththe gate electrode 1103 and the corner 303 on the right side of themulti-layer active device 200 is located beneath the gate spacer 131 tothe right of the right side of the active region 301.

As such, the interface between the active region 301 and the epitaxialgrowth of the source/drain regions 601 at the right side of themulti-layer active device 200 may have a ninth width W9 of between about8 nm and about 50 nm, such as about 10 nm, while the interface betweenthe gate electrode 1103 and the right side of the active region 301 mayhave a tenth width W10 of between about 8 nm and about 50 nm, such asabout 12 nm. Similarly, on an opposite side of the active region 301,the interface between the active region 301 and the epitaxial growth ofthe source/drain regions 601 a the left side of the multi-layer activedevice 200 may have an the seventh width W7, while the interface betweenthe gate electrode 1103 and the left side of the active region 301 mayhave an eleventh width W11 of between about 8 nm and about 50, such asabout 30 nm. However, any suitable dimensions may be utilized.

FIG. 14B illustrates a top-down view of a cross-section through thecut-line A-A of the “L-shaped” GAA transistor 1300 in FIG. 13A, inaccordance with another embodiment. FIG. 14A is similar to andillustrates the same features as FIG. 13B; however, in FIG. 14B the gateelectrode 1103, gate dielectric 1101 (not shown), and gate spacers 131are formed over the active region 301 with an offset to the right(OS-R), according to some embodiments. For ease of discussion, the gatedielectric 1101 and the CESL 87 are not shown.

According to some embodiments, the offset to the right (OS-R) is betweenabout 0 nm and about 8 nm and may be formed by shifting the design ofthe photoresist masks or else through the use of measured overlayshifts. The left channel width and the right channel width of the activeregion 301 appear shifted to the right of the corners 303 of the“L-shape” in the fin 122 by the distance of the offset to the right(OS-R). As such, the corner 303 on the left side of the multi-layeractive device 200 is located beneath the gate spacer 131 or the ILD 701to the left of the active region 301 and the corner 303 on the rightside of the multi-layer active device 200 is located beneath the gateelectrode 1103 to the left of the gate spacer 131 on the right side ofthe gate electrode 1103.

As such, the interface between the active region 301 and the epitaxialgrowth of the source/drain regions 601 at the right side of themulti-layer active device 200 may have the eighth width W8 of betweenabout 8 nm and about 50 nm, such as about 10 nm, while the interfacebetween the gate electrode 1103 and the right side of the active region301 may have a twelfth width W12 of between about 8 nm and about 50 nm,such as about 12 nm. Similarly, on an opposite side of the active region301, the interface between the active region 301 and the epitaxialgrowth of the source/drain regions 601 at the left side of themulti-layer active device 200 may have a thirteenth width W13, while theinterface between the gate electrode 1103 and the left side of theactive region 301 may have a fourteenth width W14 of between about 8 nmand about 50 nm, such as about 28 nm. However, any suitable dimensionsmay be utilized.

FIGS. 15A-15E illustrates several cell schemes comprising arrays ofmulti-layer active devices, according to some embodiments. Each of thecell schemes comprises an array of multi-layer active devices 1501incorporating one or more of the “L-shaped” GAA transistors 1300. Theflexible design and power benefits of the “L-shaped” GAA transistors1300 may be applied to a large variety of cell schemes allowing forfurther design flexibility and power savings to be built into differentcell schemes.

Referring to FIG. 15A, this figure illustrates a first cell scheme 1500formed using six of the “L-shaped” GAA transistors 1300, according tosome embodiments. The first cell scheme 1500 comprises a first fin 1522having a first complex shape including three “L-shaped” active regions301 and a second fin 1523 having a second complex shape including three“L-shaped” active regions 301, the second complex shape may be a mirrorimage of the first complex shape, according to some embodiments. Thefirst fin 1522 and the second fin 1523 may be formed in themulti-layered stack 203 (not shown) and substrate 100 (not shown) usingthe materials and processes used to form the fin 122, as set forthabove. Additionally, if desired one or more of the gate electrodes 1103may be replaced with a dummy electrode, including one or more of thegate electrodes 1103 that overlie the “L-shaped” active regions 301.

FIG. 15B illustrates a second cell scheme 1510 formed using four of the“L-shaped” GAA transistors 1300, according to some embodiments. Thesecond cell scheme 1510 comprises a third fin 1525 having a thirdcomplex shape including one “L-shaped” active regions 301, the thirdcomplex shape including an opening 1511 in the first fin 1522. Thesecond cell scheme 1510 further comprises a fourth fin 1527 having asecond complex shape including three “L-shaped” active regions 301.According to an embodiment, a first of the three “L-shaped” activeregions 301 of the second fin 1523 may have a same first active width asthe one “L-shaped” active region 301 in the first fin 1522. Furthermore,the remaining two of the three “L-shaped” active regions 301 of thefourth fin 1527 may have a same second active width less than the firstactive width. According to some embodiments, the first active width maybe between about 8 nm and about 50 nm, such as about 30 nm and thesecond active width may be between about 8 nm and about 50 nm, such asabout 10 nm. The third fin 1525, the fourth fin 1527, the “L-shaped”active regions 301, and the gate electrodes 1103 may be formed using anyof the materials and processes described herein.

FIG. 15C illustrates a third cell scheme 1520 formed using four of the“L-shaped” GAA transistors 1300, according to some embodiments. Thethird cell scheme 1520 comprises a fifth fin 1529 having a fifth complexshape including four “L-shaped” active regions 301 and a sixth fin 1531having a sixth complex shape including four “L-shaped” active regions301. According to some embodiments, the sixth complex shape may be amirror image of the fifth complex shape and the four “L-shaped” activeregions 301 may have fins widths that are progressively smaller goingfrom the left side of the fins to the right side of the fins. Forexample, the “L-shaped” active regions 301 may have a first fin widthWf1 of between about 8 nm and about 50 nm, such as about 40 nm and mayhave a second fin width Wf2 of between about 8 nm and about 50 nm, suchas about 10 nm, with the width of the fins decreasing by an interval ofbetween about 72 nm and about 102 nm, such as about 90 nm. The fifth fin1529, the sixth fin 1531, the “L-shaped” active regions 301, and thegate electrodes 1103 may be formed using any of the materials andprocesses described herein.

FIG. 15D illustrates a fourth cell scheme 1530 formed using five of the“L-shaped” GAA transistors 1300, according to some embodiments. Thefourth cell scheme 1530 comprises a seventh fin 1533 having a seventhcomplex shape including two of the “L-shaped” active regions 301 and aneighth fin 1535 having an eighth complex shape including three of the“L-shaped” active regions 301. In this embodiment the complex shapes maybe offset from each other such that the seventh fin 1533 and the eighthfin 1535 are not mirror images of each other. The seventh fin 1533, theeighth fin 1535, the “L-shaped” active regions 301, and the gateelectrodes 1103 may be formed using any of the materials and processesdescribed herein.

FIG. 15E illustrates a fifth cell scheme 1540 formed using eight of the“L-shaped” GAA transistors 1300, according to some embodiments. Thefifth cell scheme 1540 comprises a ninth fin 1537 having a ninth complexshape including four of the “L-shaped” active regions 301 and a tenthfin 1539 having a tenth complex shape including four of the “L-shaped”active regions 301. According to some embodiments, the tenth complexshape may be a mirror image of the ninth complex shape, with adjacentgate electrodes 1103 each overlying an “L-shaped” active region 301. Theninth fin 1537, the tenth fin 1539, the “L-shaped” active regions 301,and the gate electrodes 1103 may be formed using any of the materialsand processes described herein.

In each of the embodiments described above, the “L-shaped” GAAtransistors 1300 may be formed as either an n-type (NMOS) GAA transistoror else as a p-type (PMOS) GAA transistor. In addition, the embodimentsdisclosed herein may be applied in both N-FET devices and P-FET devicesto “L-shaped” GAA transistors. As such, the embodiments disclosed hereinmay be used for many power saving applications with highly flexibledesign options.

Embodiments disclosed herein are directed towards an active device 200and methods of forming the multi-layer active device 200 comprisingcomplex shaped (e.g., “L-shape”) active regions 301 within thenanostructures 901 of the multi-layer active device 200. According tothe embodiments, active regions 301 may be formed having nanostructureactive lengths L1 between corners 303 of the active regions 301. Thecorners 303 are disposed under gate spacers 131 of the active device. Atdistal ends of the active regions 301, the nanostructures 901 are formedwith different widths. According to some embodiments, the multi-layeractive device 200 may have a power savings benefit of between about 6%to about 8% as compared to an active device 200 with active regions 301that are not complex shaped. Furthermore, the multi-layer active device200 provides design flexibility allowing for many different arrangementsof the active devices.

By forming and utilizing the nanostructures 901 with “L-shaped” activeregions 301 within the nanostructures 901 of the multi-layer activedevice 200, high performance may be achieved with short channel devicesand further power savings may be achieved. Furthermore, flexible designsfor different cell types using the different embodiments of the GAAdevices with “L-shaped” corners 303 disposed beneath the gate spacers131 and/or gate electrodes as disclosed herein.

According to an embodiment, a method includes: depositing a first sheetover a semiconductor substrate; depositing a first semiconductormaterial over the first sheet; depositing a second sheet over the firstsemiconductor material; depositing a second semiconductor material overthe second sheet; patterning the first sheet, the first semiconductormaterial, the second sheet, and the second semiconductor material into afin with a first width and a second width, the first width being greaterthan the second width; removing the first sheet and the second sheet toform a first nanostructure from the first semiconductor material and asecond nanostructure from the second semiconductor material; depositinga gate dielectric layer to surround the first nanostructure and thesecond nanostructure; and depositing a gate electrode around the gatedielectric layer. In an embodiment the depositing the gate electrodecomprises forming the gate electrode at least partially over a firstcorner of the first nanostructure. In an embodiment after the depositingthe gate dielectric layer, a gate spacer is adjacent to the gatedielectric layer and at least partially over a second corner of thefirst nanostructure, the second corner being adjacent to a portion ofthe fin with the second width. In an embodiment the depositing the gateelectrode comprises forming the gate electrode at least partially over asecond corner of the first nanostructure. In an embodiment after thedepositing the gate dielectric layer, a gate spacer is adjacent to thegate dielectric layer and at least partially over a second corner of thefirst nanostructure, the second corner being adjacent to a portion ofthe fin with the first width. In an embodiment the method furtherincludes: epitaxially growing a first source/drain region adjacent thefirst nanostructure, the first source/drain region having a third width;and epitaxially growing a second source/drain region adjacent the firstnanostructure, the second source/drain region having a fourth widthdifferent from the third width. In an embodiment the first width isbetween about 8 nm and about 30 nm

According to an embodiment, a method includes: forming a multilayerstack over a semiconductor substrate, the multilayer stack comprisingfirst layers having a first material and second layers having a secondmaterial different from the first material; etching a pattern into themultilayer stack, a remainder of the multilayer stack comprising anactive region separating a first side of the remainder of the multilayerstack from a second side of the remainder of the multilayer stack, thefirst side having a first width and the second side having a secondwidth that is different than the first width; performing a wire releaseprocess to remove the first layers and form a stack of nanostructures,the stack of nanostructures having the first width at the first side andthe second width at the second side; depositing a gate dielectric layeraround the stack of nanostructures; and depositing a gate electrodesurrounding each nanostructure within the stack of nanostructures. In anembodiment the method further includes forming a first source/drainregion adjacent to the stack of nanostructures at the first side andforming a second source/drain region adjacent to the stack ofnanostructures at the second side, the first source/drain region havinga width that is greater than a width of the second source/drain region.In an embodiment a difference between the first width and the secondwidth is at most 8 nm. In an embodiment one nanostructure within thestack of nanostructures comprises a first corner at the first side andthe first corner is located at least partially beneath the gateelectrode. In an embodiment the one nanostructure comprises a secondcorner at the second side and the second corner is located at leastpartially beneath the gate electrode. In an embodiment the onenanostructure comprises a second corner at the second side and thesecond corner is located at least partially beneath an interlayerdielectric, wherein the first width is larger than the second width. Inan embodiment the one nanostructure comprises a second corner at thesecond side and the second corner is located at least partially beneathan interlayer dielectric, wherein the first width is smaller than thesecond width

In an embodiment, a device includes: a gate dielectric over a substrate;a gate electrode around the gate dielectric; and a vertical stack ofnanostructures, each nanostructure of the vertical stack ofnanostructures comprising an active region being surrounded by the gatedielectric, wherein each of the active regions comprises a first channelwidth on a first side of the gate dielectric and a second channel widthon a second side of the gate dielectric, the first channel width beinggreater than the second channel width. In an embodiment the firstchannel width is no greater than 16 nm larger than the second channelwidth. In an embodiment a first nanostructure of the vertical stack ofnanostructures comprises a first corner on the first side of the gatedielectric and a second corner on the second side of the gatedielectric. In an embodiment the device further includes: a first gatespacer disposed adjacent the gate electrode on the first side of thegate dielectric; and a second gate spacer disposed adjacent the gateelectrode on the second side of the gate dielectric. In an embodimentthe first corner is disposed at least partially beneath the first gatespacer and the second corner is disposed at least partially beneath thegate electrode. In an embodiment the first corner is disposed at leastpartially beneath the gate electrode and the second corner is disposedat least partially beneath the second gate spacer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: depositing a first sheetover a semiconductor substrate; depositing a first semiconductormaterial over the first sheet; depositing a second sheet over the firstsemiconductor material; depositing a second semiconductor material overthe second sheet; patterning the first sheet, the first semiconductormaterial, the second sheet, and the second semiconductor material into afin, wherein a topmost surface of the fin has both a first width and asecond width in a top-down view, the first width being greater than thesecond width, and the first width being measured along a first directionparallel to a second direction that the second width is measured along;removing the first sheet and the second sheet to form a firstnanostructure from the first semiconductor material and a secondnanostructure from the second semiconductor material; depositing a gatedielectric layer to surround the first nanostructure and the secondnanostructure; and depositing a gate electrode around the gatedielectric layer.
 2. The method of claim 1, wherein the depositing thegate electrode comprises forming the gate electrode at least partiallyover a first corner of the first nanostructure.
 3. The method of claim2, wherein after the depositing the gate dielectric layer, a gate spaceris adjacent to the gate dielectric layer and at least partially over asecond corner of the first nanostructure, the second corner beingadjacent to a portion of the fin with the second width.
 4. The method ofclaim 2, wherein the depositing the gate electrode comprises forming thegate electrode at least partially over a second corner of the firstnanostructure.
 5. The method of claim 4, wherein after the depositingthe gate dielectric layer, a gate spacer is adjacent to the gatedielectric layer and at least partially over the second corner of thefirst nanostructure, the second corner being adjacent to a portion ofthe fin with the first width.
 6. The method of claim 1, furthercomprising: epitaxially growing a first source/drain region adjacent thefirst nanostructure, the first source/drain region having a third width;and epitaxially growing a second source/drain region adjacent the firstnanostructure, the second source/drain region having a fourth widthdifferent from the third width.
 7. The method of claim 1, wherein thefirst width is between about 8 nm and about 30 nm.
 8. A methodcomprising: forming a multilayer stack over a semiconductor substrate,the multilayer stack comprising first layers having a first material andsecond layers having a second material different from the firstmaterial; etching a pattern into the multilayer stack, a remainder ofthe multilayer stack comprising an active region separating a first sideof the remainder of the multilayer stack from a second side of theremainder of the multilayer stack, wherein a topmost surface of theremainder of the multilayer stack has both a first width and a secondwidth in a top-down view, wherein the second width is different from thefirst width, wherein the first width is measured along a first directionparallel to a second direction that the second width is measured along,the first width corresponding to the first side of the remainder of themultilayer stack and the second width corresponding to the second sideof the remainder of the multilayer stack; performing a wire releaseprocess to remove the first layers and form a stack of nanostructures,the stack of nanostructures having the first width at the first side andthe second width at the second side; depositing a gate dielectric layeraround the stack of nanostructures; and depositing a gate electrodesurrounding each nanostructure within the stack of nanostructures. 9.The method of claim 8 further comprising forming a first source/drainregion adjacent to the stack of nanostructures at the first side andforming a second source/drain region adjacent to the stack ofnanostructures at the second side, the first source/drain region havinga width that is greater than a width of the second source/drain region.10. The method of claim 8, wherein a difference between the first widthand the second width is at most 8 nm.
 11. The method of claim 8, whereinone nanostructure within the stack of nanostructures comprises a firstcorner at the first side and the first corner is located at leastpartially beneath the gate electrode.
 12. The method of claim 11,wherein the one nanostructure comprises a second corner at the secondside and the second corner is located at least partially beneath thegate electrode.
 13. The method of claim 11, wherein the onenanostructure comprises a second corner at the second side and thesecond corner is located at least partially beneath an interlayerdielectric, wherein the first width is larger than the second width. 14.The method of claim 11, wherein the one nanostructure comprises a secondcorner at the second side and the second corner is located at leastpartially beneath an interlayer dielectric, wherein the first width issmaller than the second width.
 15. A device comprising: a gatedielectric over a substrate; a gate electrode around the gatedielectric; a vertical stack of nanostructures, each nanostructure ofthe vertical stack of nanostructures comprising an active region beingsurrounded by the gate dielectric, wherein a topmost surface of each ofthe active regions comprises: a first channel width on a first side ofthe gate dielectric; and a second channel width on a second side of thegate dielectric, the first channel width being greater than the secondchannel width, wherein the first channel width and the second channelwidth are measured along directions that are parallel to each other. 16.The device of claim 15, wherein the first channel width is no greaterthan 16 nm larger than the second channel width.
 17. The device of claim15, wherein a first nanostructure of the vertical stack ofnanostructures comprises a first corner on the first side of the gatedielectric and a second corner on the second side of the gatedielectric.
 18. The device of claim 17 further comprising: a first gatespacer disposed adjacent the gate electrode on the first side of thegate dielectric; and a second gate spacer disposed adjacent the gateelectrode on the second side of the gate dielectric.
 19. The device ofclaim 18, wherein the first corner is disposed at least partiallybeneath the first gate spacer and the second corner is disposed at leastpartially beneath the gate electrode.
 20. The device of claim 18,wherein the first corner is disposed at least partially beneath the gateelectrode and the second corner is disposed at least partially beneaththe second gate spacer.